Effects of Salicylic Acid on Some Physiological and Biochemical Attributes of Medicinal Pumpkin under Drought Stress

Oxidative stress is one of the most important consequences of drought stress. Salicylic acid is a phenolic compound which serves as a growth regulator in the induction of resistance to drought. In order to investigate the role of salicylic acid on some Anti-oxidant Enzymes and some biochemical attributes of medicinal pumpkin under drought stress, an experiment was designed 2014 in Zanjan University’s Research Farm. The study was arranged as factorial experiment based on a randomized complete block design with three replications including drought stress at four level; control, mild stress, moderate stress, and severe stress have been arranged in four levels including (100, 85,70 and 55%FC). Salicylic acid treatments included Salicylic acid were applied as foliar application spray in 4 levels: zero mg/l (solution spray with distilled water), 0.5, 1, and 1.5 mg/l. Measured traits that included peroxidase, catalase, Beta-sitosterol and oil yield proline, electrolyte leakage, malondialdehyde (membrane peroxidation index) content. The results showed that increasing drought stress levels reduced the oil yield, but in contrast, increased the Beta-sitosterol, membrane peroxidation, electrolyte leakage, anti-oxidant enzymes such as catalase and peroxidase, while application of salicylic acid at 0.5 and 1 mg/l decreased oxidative stress, membrane peroxidation and Electrolyte leakage through increasing the anti-oxidant enzymes activities such as catalase and peroxidase and proline which led to a balanced rise in oil yield and Beta-sitosterol in mild and moderated stress. These results shows an increase in plant resistance to drought as a result of salicylic acid application.